SYNTHESIS OF FATTY-ACIDS SPECIFICALLY LABELED WITH C-11 IN VARIOUS POSITIONS, INCLUDING H-2 SUBSTITUTION, FOR IN-VIVO STUDIES OF MYOCARDIUM USING PET

Fatty acids were labelled with C-11 in several positions by reacting [C-11]carbon dioxide with the appropriate Grignard reagent or by reacting a alpha,omega-bis-(bromo magnesium) alkane with a C-11-labelled alkpl iodide followed by a reaction with carbon dioxide. The methyl and methylene C-11-labelled fatty acids were obtained in 12-36% (decay corrected) radiochemical yield within 45-65 min, and with radiochemical purities higher than 96%. Perdeuterated alpha,omega-dibromo hexane, decane and tetradecane were synthesized from dimethylacetylene dicarboxylate by means of a Raney-nickel reduction in D2O, Kolbe electrolysis and LAD reduction. The use of multiple isotopic labelling by the combination of position specific C-11 labelling and H-2 substitution, has the potential to highlight different aspects of a complex biochemical system by PET. This principle is illustrated by results of the kinetics of different types of C-11 label of dodecanoic acid and the corresponding moieties of acetate. The combination of tracers allows the kinetics of beta-oxidation of middle length carbon chain fatty acids and citric acid cycle metabolism to be separately assured, whilst deuteration of the tracers opens the possibility of highlighting the kinetics of the proton extraction processes reflecting rate limiting steps.